Figure 8-3.-Plastic pipe fittings.
PLASTIC PIPE.— Plastic pipe has seen
extensive use in current Navy construction.
Available in different lengths and sizes, it is lighter
than steel or copper and requires no special tools
to install. Plastic pipe has several advantages over
metal pipe: it is flexible; it has superior resistance
to rupture from freezing; it has complete
resistance to corrosion; and, in addition, it can
be installed aboveground or belowground.
One of the most versatile plastic and polyvinyl
resin pipes is the polyvinyl chloride (PVC). PVC
pipes are made of tough, strong thermoplastic
material that has an excellent combination of
physical and chemical properties. Its chemical
resistance and design strength make it an excellent
material for application in various mechanical
systems. Sometimes polyvinyl chloride is further
chlorinated to obtain a stiffer design, a higher
level of impact resistance, and a greater resistance
to extremes of temperature. A CPVC pipe (a
chlorinated blend of PVC) can be used not only
in cold-water systems, but also in hot-water
systems with temperatures up to 210°F.
Economy and ease of installation make plastic
pipe popular for use in either water distribution
and supply systems or sewer drainage systems.
GALVANIZED PIPE.— Galvanized pipe is
commonly used for the water distributing pipes
inside a building to supply hot and cold water to
8-3
the fixtures. This type of pipe is manufactured
in 21-ft lengths. It is GALVANIZED (coated with
zinc) both inside and outside at the factory to
resist corrosion. Pipe sizes are based on nominal
INSIDE diameters. Inside diameters vary with the
thickness of the pipe. Outside diameters remain
constant so that pipe can be threaded for
standard fittings.
CAST-IRON WATER PIPE.— Cast-iron
pipe, sometimes called cast-iron pressure pipe, is
used for water mains and frequently for service
pipe up to a building. Unlike cast-iron soil pipe,
cast-iron water pipe is manufactured in 20-ft
lengths rather than 5-ft lengths. Besides bell-and-
spigot joints, cast-iron water pipes and fittings are
made with either flanged, mechanical, or screwed
joints. The screwed joints are used only on small-
diameter pipe.
Fittings
Fittings vary according to the type of piping
material used. The major types commonly used
in water service include elbows, tees, unions,
couplings, caps, plugs, nipples, reducers, and
adapters. Some typical copper pipe fittings are
shown in figure 8-2. Plastic pipe fittings (fig. 8-3)
that are similar in appearance to those used with
metal piping are available. Some plastic pipes can
